Cocaine use can lead to a number of short-term symptoms, including rapid heart rate, increased energy and sense of alertness, and even massive heart attacks. It affects the brain, and elicits some of these symptoms, by causing the build-up of dopamine in the brain, which causes extremely pleasurable sensations.
The drug's long term effects can include high blood pressure, stroke, rapid weight loss, paranoia and hallucinations, and severe, sometimes violent mood swings. But by far the most common long term effect is actually addiction, which can be both physical (i.e. chemical) and mental. Scientists have linked the highly addictive nature of cocaine to the very process that makes it so pleasurable, the release of dopamine.